The present invention relates generally to a wide-angle optical system and an imaging apparatus incorporating the same, and more particularly to a wide angle-of-view, small-format optical system capable of relatively close range photography.
With recent slimming-down of cellular phones, personal digital assistants, notebook computers or the like, there are now mounting demands for camera modules having an optical system curtailed to the limit in its optical axis direction length. To meet such demands, there are many single-focus optical systems proposed which are made up of two or three aspheric lenses at most.
In recent years, there have also been imaging devices developed in which even when light is obliquely incident on their peripheral sites, their sensitivity does not drop, and with this, the exit pupil position of an associated optical system can be brought close to an image device side so that the total length of the optical system can be shortened. Among optical systems having a reduced total length so far proposed in the art, there are the ones of Patent Publications 1, 2 and 3 showing that three lenses are used and the exit pupil position is brought close to the imaging device side.
Patent Publication 1: JP(A) 2007-3768
Patent Publication 2: JP(A) 2007-47513
Patent Publication 3: JP(A) 2007-58153